A 3D display device and a manufacturing method thereof are provided. Metal nanowires perpendicular to each other are provided at the TFT glass substrate side and the CF glass substrate side. The metal nanowires can realize inherent function of polarizers at the TFT glass substrate side and the CF glass substrate side, and can also make the emitted light into stripe-shaped polarized light perpendicular to each other. Therefore, the polarizers, the λ/2 phase retarder with stripes, and the polarizers with stripes and perpendicular polarization that are originally at the TFT glass substrate side and the CF glass substrate side in a 3D polarizer display are excluded. The thickness of the 3D display device is made thinner. Moreover, according to the structural design, polarization effect is not limited by wavelength range of the light. Therefore, 3D stereoscopic display effect is greatly enhanced.